INSULIN-SECRETION AND SENSITIVITY IN NEWLY-DIAGNOSED NIDDM CAUCASIANSIN THE UK

Beta-cell secretion and insulin sensitivity was studied in healthy sub jects and newly diagnosed Caucasian (Welsh) NIDDM patients. A standard ized meal tolerance test (MTT) and frequent sampled intravenous glucos e tolerance tests (FSIVGTT) were employed and the patients stratified according to fasting plasma glucose (FPG). A deficient early (first ho ur) post-prandial (MTT) insulin secretion was demonstrated in all NIDD M patients, deteriorating with increasing fasting hyperglycaemia. For the patient group fasting and post-prandial hyperproinsulinaemia was e vident with diminishing post-prandial excursions as fasting hyperglyca emia increased. The early phase (0-10 min) insulin secretion to intrav enous glucose (300 mg kg(-1)) was severely impaired in NIDDM patients. A short-lived paradoxical fall in plasma insulin concentrations was o bserved in those with FPG >9 mmol l(-1). Insulin sensitivity utilizing the insulin modified FSIVGTT demonstrated that all NIDDM patients had marked insulin insensitivity. Characteristic of the newly diagnosed p reviously untreated Caucasian NIDDM is a dysfunctional beta cell, resu lting in a deficit in insulin secretion with relative hyperproinsulina emia. The quantitative and qualitative secretory status of the beta ce ll decreases with increasing fasting hyperglycaemia. Insulin sensitivi ty is markedly reduced when FPG exceeds 7.0 mmol l(-1) with little or no further discernible fall with deteriorating glycaemic control.